Long duration flights in Venus’ atmosphere using passive solar hot air balloons

Abstract

Solar balloons are a promising platform for providing multi-hour flights in and above the upper cloud layer of Venus. The temperature and pressure profiles from 55–75 km above the surface of Venus are very similar to Earth’s from sea level to approximately 30 km, the site of numerous terrestrial solar balloon missions. Additionally, Venus’ highly reflective cloud layer can provide a higher intensity of reflected solar radiation. An ideal solar balloon envelope incorporates a lightweight material that has a high absorbtivity in the visual spectrum, and a low emissivity in the infrared spectrum. The envelope then absorbs direct, reflected, and diffuse radiation, as well as infrared radiation, and heats up the internal balloon air through conduction, resulting in passive flight without the need for an external heat source or lifting gas. This work builds on previous high altitude and solar balloon models and adapts them for Venus’ atmosphere to explore their expected payload mass capacity and flight times. The possible equilibrium float altitudes for various system masses and solar zenith angles are compared between Earth and Venus. Finally, an Earth simulation is compared to terrestrial solar balloon mission data to validate the model and further demonstrate the feasibility of solar balloon flight on Venus.